\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, yscale=.5,inner sep=1pt]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw (0,0) to [battery2] (2,0) to [cute open switch](4,0)--(5,0)--(5,1.5)--(0,1.5)--(0,0);
  \draw (0,2)--(5,2)--(5,3.5) to [rmeter, t=G](0,3.5)--(0,2);
  \node at (-.25, 1.5)[below]{$A$};
  \node at (-.25, 2)[above]{$C$};
  \node at (5.25, 1.5)[below]{$B$};
  \node at (5.25, 2)[above]{$D$};
  \node at (3, -.5){$K$};
\end{circuitikz}
\end{document}